Modbus TCP diagnostics

Hello, I am building an application that communicates with plc through modbus tcp.
I can read registers and coils, with all commands (1-4).
My problem is that I have not found a way to get diagnostics messages from plc. Modbus_TCP_Standard refairs in fc 08 command..

My questions are,
1. DOes this commands works really under modbus tcp? Ι read modbus rtu and says that diagnositcs do not work at modbus tcp
2. HAve you any idea, what command should I send to get communication messages ?

Best regards

Standard says fc8 is for diagnostics in vendor specific devices. Does your PLC support this function? Usually no, at least I haven't seen one.
So then you have to program some diagnostics and send the status data in the registers that you can access.

I agree. Rarely are diagnostics implemented.

Thanks both of you...